Been busy virtually assembling this printer I called ZideX. Sharing it here hoping to get some feedback, a constructive one please 
Quick description:
extrudes one at a time while the other extruder parks
why dont you use linear rails?
also i think now the trend is to use a mixer and have a single hotend. this makes calibration simpler tho it would be difficult to print different materials (do you want that?)
It looks a bit to small.
I love that you are trying to make a compact printer but I’m not sure about the platform size
Linear rail is too loud.
Yes platform is small due to most things I printed actually can all fit in that small bed
No mixer due to want to print PLA / PVA combo
cool setup but i think it can be simpler with a single z axis. any reason for the separate z?
It looks cool but in my opinion, it’s overly complicated and over built. It reminds me of a midget muscle builder. I will say that I wish I could build my own 3D printer. That would be sweet. I’ve been thinking about taking my current one apart and rebuilding it with better parts. It’s not very sturdy but works ok for what it is.
David that is the part that I’m still unsure. Ideally I wanted the z to be separate and have its own endstop. I’ve started looking into duet wifi and it appear the beta firmware support 2 separate z endstop. I won’t know until I build it I gues…
If not, like you said I’ll have to settle with 1 z motor driving two leadscrew.
Looks really cool, at least 
Why the big pulley reduction on the Z screws? A shallower thread pitch accomplishes the same thing with fewer parts.
You’ll want to use a self-locking screw pitch (like Tr8x2) for a “crane” style printer like this, so the nozzle doesn’t crash into the bed on power-off. A 2mm/rev screw is already plenty high-power and slow, any more gear reduction will just make it craaaaaawl for no benefit.
Ryan I plan on sourcing most of these parts from openbuilds and they happen to carry Tr88 and its nut block was the key to make the build compact. I think with 60t to 20teeth pulley reduction it should perform similar to Tr82. not sure if the conversion is that straight forward…
@Step_Cia 20t/60t would be the equivalent of a Tr82.67 so it will be slightly faster than a Tr82 however Ryan has a very valid point: why complicate the design with the belt and 2 more pulleys when you can use something out of the box?
the block nut is for Tr88 and they are slim so I can hide it behind the Z plate carriage. Not sure if I can find something similar for Tr82…
you mean this one: https://www.robotdigg.com/product/1040/POM-Nut-Block-for-8mm-Lead-Screw ?
oh interesting… it might just work if I can only find where is the dimension…
Tr8x8 will back-drive unless there’s a lot of preload/friction on the Z stage. You don’t want your ZX crane stage back-driving on power-off, unpleasant things can happen. If you do crank up the friction (eg over-tightening v-wheels) then you won’t want to do bi-directional Z motion, eg bed tilt correction or mesh leveling. Anti-backlash nuts can add friction AND allow bi-directional motion, but it’ll wear and slow down the Z stage to keep the motor at an RPM range where it isn’t losing too much torque.
I really think your best bet here is to buy a 2mm screw with integral motor, it’s much simpler and will perform better than a 2.6666… mm/rev or 8mm/rev screw for this kind of printer.
http://2.6666…mm/rev on a 1.8 degree stepper comes out to 0.01333… mm per fullstep, so good luck picking printing layer heights that are multiples of full steps…
Ryan took a while to digest your last comment. I think I understand your point and thanks for pointing it out.
while keeping Tr8*8 If I swapped the 60t pulley with 40t then I will have 0.02 mm per full step so as long as my layer height is an even number I will be fine
even better is like you said use Tr8*2 then I can use even and odd layer height since mm per full step would be 0.01
Have you looked into if the combined catalever is heavier than the base?
I have not… I think the base would be slightly heavier but not by much.
It’s nice
